Nikon D40x I can turn it on but doesn't take a photo.

While viewing the photo, press cursor-up/down to cycle through the different views of your photo.

Can you upload a photo that shows this? You can just take one set to low resolution so the file size isn't too big.

PUT YOUR MEMORY SD CARD INTO CARD READER THEN UPLOAD PHOTO,S

It sounds like your flash capacitor isn't fully charged up and your taking a photo and there isn't enough power charged up, so your photos turn out too dark. Take a photo, wait for a minute or til you see the flash icon inside the viewfinder lit up and then try taking another photo.

Pull up the photo in image view, then use the up arrow until the flashing stops.

Push ring circling OK button to up or down positions and LCR display will change showing info or image. 

to turn this setting off just press the down arrow button when reviewing your photos. you will scroll through a number of ways to view tho photo including histogram, and one of the settings is just the picture.

conorp, not on a D40. This camera does not have the "Live View" capability.

Try formatting the card then using it again. Does this work?

Does the computer see the camera when you plug it in?